When drip irrigation systems are buried underground, problems can arise when the water pressure is shut off. There are two scenarios: Most drip irrigation emitters will allow the water in the tube to run out into the soil when the water pressure is off. This results in a vacuum in the tube, causing soil to be sucked back into another emitter, thereby plugging the second emitter. To avoid this risk, almost all buried drip systems are fitted with vacuum relief valves. When the slope is monotonic this is a comparatively simple matter, albeit, not costless. However, if the slope is undulating or complex, then the positioning of vacuum relief valves can be both difficult and expensive. In special conditions, such as on golf courses, especially putting greens, the presence of vacuum relief valves may be unacceptable.
Some drip irrigation valves are designed in such a manner that the valve shuts off when the water pressure is off, thereby sealing the water in the tube until the next operating cycle. The problem with this type of emitter is that if the water contains any biological matter, bacteria may multiply and form slimes that will block the emitter on the next cycle.
My invention solves these problems. Experimental tests of my invention demonstrate that the anti-syphon emitter causes the supply tube to empty slowly when water pressure is shut off, thereby inhibiting undesired build up of vacuum pressure in the tube. The anti-syphon emitter also avoids the bacteria problems caused by maintaining water sealed inside the tube when the valve shuts off.
There are many pressure compensating emitters on the market. These include a rubber diaphragm which moves forward under pressure to seal against a rim to provide a controlled flow. Mehoudar U.S. Pat. No. 4,209,133 describes such an emitter. Another such emitter is described in Mehoudar U.S. Pat. No. 6,206,305. Mehoudar U.S. Pat. No. 4,209,133 is an emitter of the first type above. Mehoudar U.S. Pat. No. 6,206,305 is adaptable to be of the second type. The disclosures of the '133 and '305 patents are incorporated herein by reference.